please tell me which option should be used in the following cases? and Have you got any rules for this?
1. Not only Mary but also I ( am/ is /are) students
2. Not only her parents but also her grandma (like/ likes) the film
Thanks a lot.
(1) According to the books, the "rule" is to make the last verb agree with the last item.
(2) Here are two examples from a very reliable book: Not only the chairs but also the TABLE WAS sold./ Not only the table but also the CHAIRS WERE sold.
(3) Perhaps your first sentence should be something like: Not only Mary but also I AM A STUDENT/ Not only Mary but I am a student/ Not only Mary but I also am a student. In conversation, perhaps: Mary and I are students/ Both Mary and I are students/ Mary is a student, and I am, too.
(4) Perhaps your second sentence should be: Not only her parents but also her GRANDMA LIKES the film.
(5) Please remember that native speakers don't always follow the rule.